Grinding disk-cutter and apparatus therefor



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--(N0'Mode1.) Y A.V JOHNSTON. GRINDING DISK SUTTENS AND APPARATUS THBRNPOR.

Patent'edSe'pt. 5, v1893.

I' nomi/snee@ 3! TON.

A(No Mdel.)

APBARATUS THB-1151103, Patented'Sept, 1893.

- A.- J0 GRINDING DISK GUTTER-S No. 504,386.

4 Sheets-Sheep 4.

A. JOHNSTON. GRINDING DISK CUTTERS AND APPARATUS THEREFOR. 11%. 504,386.

Patent-ed Sept.. 5,1893.

UNITED STATES PATENT OFFICE.

ALLEN JOHNSTON, OF OTTUMWA, IOWA.

GRINDING DISK-CUTTER AND APPARATUS THEREFOR.

SPECIFICATION formingpart of Letters Patent No. 504,386, dated September 5, 1893.

Application filed June 15, 1892.

To all w22/0m it may concern:

Be it known that I, ALLEN JOHNSTON, of Ottumwa, in the county of Wapello and State of Iowa, have invented a new and useful Improvement in Grinding Disk-Cutters and Apparatus Therefor, which is fully set forth in the following specification.

This invention has reference to grinding convex, concave or straight metal surfaces, and has particular reference to the grinding of disk-shaped saws orcutters which are used for cutting slots-such as the nicks in screwheads,-and for other purposes. These cutters are ground on their faces to a slight concavity, so that they are somewhat thicker at their outer toothed edges than at the center. Sometimes, for special work, the disks are ground convex on both faces, or concave on one side and convex on the other.

The invention has reference more generally to the grinding of steel disks from plane surfaces to a concave, convex or concavo-convex form. The operation of grinding these disks or cutters is a diflicult and costly process, requiring skilled workmen, and is the chief item of expense in the manufacture of these articles. This may be most clearly indicated by stating that a disk-cutter, made, tempered, and in all respects finished to the point of grinding, is worth about ten cents, Whereas, after its faces are ground to the desired form, it is Worth eight or nine times that amount. The present practice is to hold the disk-cutter or blank by a chuck which engages in the central opening thereof, and present its facev to the edge of a grinding wheel. The wheel and disk are rotated in planes substantially at right angles to each other. The disk must be fed across the edge of the grinder so that the latter may act on all points of the formers surface, and great care and skill must be exercised to secure a uniform bevel from the edge inward, and to remove just the right amount of metal. When one side is ground the disk is removed from the chuck, its position reversed, and the other side ground in the same manner. Not only is this method tedious, but considerable time is lost in chucking and unchucking the disks, so that the grinding of one disk an hour is a fair average for an ordinary workman.

The general objects of the present invenwheel.

Serial No. 436.854. (No model.)

tion are to expedite and cheapen the process of grinding these disks, to enable them to be ground with certainty to the exact shape desired and by unskilled workmen, and to dispense with the necessity of using a chuck and of feeding the disk laterally during the grinding operation. I accomplish these results in the following way: The disk is presented to the grinding wheel, not in a plane at right angles to the face of the wheel, as heretofore, but in a plane substantially parallel to the face of the If exactly parallel the work will be ground fiat, but if slightly oblique it will be concave or convex, the amount of Obliquity determining the arc of concavity or convexity to be given to the disk. lf that edge of the disk which overlaps the wheel is inclined away from the latter, the disk will be ground concave; but if inclined toward it, the disk will be ground convex, the amount of concavity and convexity being proportional to the angle of inclination. If parallel it will be ground straight. Assuming the, grinding to be concave, the corner of the grinder acts first on the inner edges of the annular disk, and the latter is fed forward (or the wheel may be advanced) as the grinding proceeds, until the grinder has hollowed out the entire face of the disk. The disk is not displaced laterally with respect to the axis of the wheel. By this process unskilled workmen are able to grind disks at an average of ten an hour, and over. Preferably Ithe grinding is effected by means of a soft cup-shaped or hollow grinding wheel in conjunction with watersubstantially as described in my Patent No. 465,37 6, dated December l5, 1891. To save time now lost in securing the disk by a chuck and releasing it therefrom, I provide'a holder which consists essentially of a head which fits the finished disk (being either convex or concave) and a circular or ring shaped projection which loosely holds the disk and prevents its lateral displacement. This proj ectionmay be a boss adapted to fit into the central opening of the disk, or where the latter is very thin, it may bearing which encircles the disk; These devices are regarded as the equivalent one of the other. When a plate or disk'is ground flat a `chuck may be employed.

The. greatest advantages of the invention are realized when the face of the disk or plate is to be ground to a curved surface; but the invention is also useful when grinding a4 straight or flat surface. Vhen such surfaces are ground on the edge of the wheel, instead of on the face thereof, the plate or disk must be fed laterally across the grinding edge, there being only a single line of contact, and at first only a small portion of the surface being ground is in contact with the wheel,causing excessive grinding action at that part. Another consequence is that the piece being ground is heated and expanded unequally at different parts, more metal being removed at the heated and expanded places, so that when the piece cools and assumes its normal shape an uneven and untrue surface is the result. On the other hand when the piece is ground according to the present invention, that is, placing it against and overlapping the face of the grinder, and then revolving it in contact with said face, the necessity for lateral feeding is dispensed with, and every point of the surface of the metal piece is acted upon by the grinding wheel at each revolution of the former; whereby the difficulties above referred to are obviated, and a surface is ground more nearly true than could be obtained in any other Way. It will be readily understood that the revolution of the disk while being ground distributes the heat, generated by the grinding, over the entire disk, and the action is at all times uniform; whereas, in the old method of grinding, the heat was localized at the part in contact with the Wheel, the extent of contact being at irst very small and constantly varying as the disk was fed across the edge of the wheel.

In order that the invention may be more fully understood, I will describe the same in connection with the accompanying drawings, which illustrate a machine designed to be used in grinding disks according to the invention.

Figure I, is a front elevation of the machine; Fig. II, a plan view thereof, partly in section. Figs. III and IV are enlarged details illustrating the grinding of a concave and of a convex disk respectively. Fig. V, is a detail in elevation illustrating the relative positions of the disk and grinding wheel, and Figs. VI and VII are respectively an elevation and a horizontal section showing a piece being ground to a straight surface.

In the drawings A is a trough adapted to contain water, and is supported upon a pedestal A and partly covered by a hood B.

C is the cup-shaped grinding wheel mounted on a horizontal arbor C', having fast and loose pulleys o, c. Wheel C is covered by hood B and is also partly protected in front by a vertical guard plate B. Water is conducted to the interior of the wheel by a trough D and is spread by centrifugal force over the grinding surface of the wheel.

E is a horizontal table, supported by a bolt e which passes up through a sleeve F resting on the bottom of trough A. Table E can thus turn horizontally on its center. An adjustable plate G rests on table E, said plate having cross-slots ff', which are intersected by a longitudinal slot e in said table. Through table E and through the points of intersection of the said slots, pass holding bolts g, and the plate G is secured to table E during the operation of grinding by means of the bolts and the nuts g. Plate G carries a sleeve I-I, which is fast th ercon, and within the sleeve H is another sleeve I, provided with a feather 7J, which lies in a groove in the outer sleeve, so that sleeve I can slide longitudinally but cannot rotate.

Sleeve I constitutes the bearing for a hollow spindle K, which carries at its outer end a driving pulley K and at its inner end a plate L, against which the disks are held while being ground. To prevent lateral displacement of the disk, the plate L has a projecting boss Z, as shown in Figs. II, III, and IV which is adapted to tit in the central opening of the disk M. If the latter is very thin,

or has no hole in it, I use instead of boss l a projecting ring Z', which encircles the disk. Whichever of these arrangements be used, it is evident that the operation of slipping a disk onto the holder, or removing it therefrom, may be very quickly performed. The sleeve I is encircled near its outer end by a hand-wheel N, whose hub n is screw-threaded externally and engages threads in the fixed sleeve H. By turning wheel N the sleeve I, and with it the Work holder, may be moved lengthwise toward and from the grinding wheel C. It is obvious that devices of various kinds may be used to eifect these adjustments.

The work-holder may be adjusted toward and from the axis of the grinder by means of slot e', and may be turned more or less obliq uely to the face of the grinder by means of the cross slots ff. As shown in Fig. V, the outer corner p of the face of the grinder C intersects the central opening m of the disk or cutter M. Consequently the grinding takes place on both sides of this central opening. If the side m of the disk which is nearest the axis of the grinder,be inclined away from the latter, as shown in Figs. II and IILa concave face will be ground upon the disk. The grinding will begin at the edge of the central opening m, which at first is the only part that touches the face of the grinder, and will continue until the entire face of the disk is hollowed out. The degree ot' concavity will depend upon the angle of inclination of the disk M from the face of the grinder. When the Work is to be ground concave, the bearing plate L of the work-holder is made convex to t the shape of the finished disk, so as to furnish a perfect support therefor.` The disk is placed upon its holder and advanced by Wheel N into contact with the grinder, and the disk and grinder are then rotated, preferably in opposite directions. Since the disk has a iiat face in contact with the convex bearing plate L, the former would have a tendency to spring,

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as the grinding proceeds farther and fartherfrom the center of the disk. To avoid this the disk after being partly ground on one face, is reversed and ground to the same extent on the other until the grinding is complete. Thus the disk is always supported by the bearing plate opposite or nearly opposite to the line of action of the grinder. If the side fm of the disk (Fig. V) be inclined toward the grinder 1o (as in Fig. 1V), the result will be a convex surface, the grinding beginning at the outer edge. In this case the bearing plate L should have a concave surface, as shown in Fig. IV. The method of reversing the disk at interr 5 vals is employed for the same reason as in the grinding of concave disks. The disk is fed in the direction of its axis of rotation as the grinding proceeds; but the feeding forward of the grinding wheel would be an equivalent Azo operation. Y

When the work is to be ground vfiat it is presented parallel to the face of the grinder. This operation is indicated in Figs. VI and VII. The work M2, which in this case is a z5 rectangular plate, is held between the chuckjaws Q carried by the spindle K, by which the work holder is rotated as in the other figures. The chuck jaws are adjusted by screws q in a well known manner. From these figures' it 3o will readily be seen that at each revolution Aof the plate M2 every point of its surface willv be acted upon by the grinder C, and that the pressure (which is the same whether a small orlarge surface of the work bears against the 3 5 grinder), and also the heat generated by friction, are evenly distributed.

Having now fully described my invention, what I claim is l. The described method of grinding the 4o face of a disk or plate, by presenting it in contact with the circular face of a grinder with the wheel overlapping and embracing about half the work, the rest of the surface of the latter projecting beyond the outline of the wheel, and rotating the work in such man- 5o out the operation, substantially as described.

2. The method of grinding the face of a disk to a curved surface, by presenting the disk to the face of a grinding wheel at an angle slightly oblique to said face, and rotating the disk against the grinding face, substantially as described;

3. The method of grinding the face of a i metal disk to a curved surface, by presenting the disk to the face of a grinding wheel so that about half the surface of the disk overlaps the face of the Wheel, said disk being inclined at a slight angle with said face, rotating the disk, and feeding it in the line of its axis of rotation as the grinding proceeds, substantially as described.

4. The method of grinding a disk-such as a slot cutting'tool-to a curved surface, which method consists in presenting the face of the disk to the face of a grinding wheel at a slight angle with said wheel, grinding a portion of the face of the disk against the corner of the wheel, then reversing and partly grinding the other face, and so proceeding until the grinding is completel on both sides, substantially as described.

5. In a machine for grinding metal disks to a concave, straight, or convex surface,l the combination with the grinding wheel of a work-holder adapted to hold the disk against the face of the grinding wheel and mounted on a support which is adjustable to present the face of the work holder at dierent angles or parallel toI the face of said wheel, means for rotating said work-holder on its axis, and means for moving it in line of its axis while the grinding proceeds, substantially as de-y scribed.

6. The combination with the grinding wheel, of a rotatable work-holder adapted' to present the work against the face of the grinding wheel, and comprising a bearing plate and a circular projection adapted to engage the edge of vthe work, a support for said workholder adjustable on an axis transverse to the axis of the grinder, means for rotating the work-holder, and means for moving it toward and from the face of the grinding wheel, l

substantiallyas described.

7. The combination with the grinding wheel, of a table for supporting the work-holding devices, a plate adjustable axially and also adj ustable transversely with respect to the face of the grinding Wheel, a rotatable bearingplate adjustable in its support in the line of its axis, and a holding projection on the face of said plate, substantially as described.

In testimony whereof I have signed this specification in the presence of two-subscribing witnesses.

ALLEN JOHNSTON.

Witnesses:

A. G. HARRow, J. T. HACKWORTH.

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